1. Field of the Invention
The present invention relates to a spin chuck for holding and rotating a substrate to be treated, such as a semiconductor wafer or an LCD substrate, and to a treatment apparatus using the spin chuck.
2. Description of the Related Art
An apparatus for cleaning a semiconductor wafer is known as a treatment apparatus using a spin chuck. In this type of cleaning apparatus, a wafer is held in a horizontal position and rotated by the chuck. While the wafer is being rotated, a surface of the wafer is supplied with a cleaning liquid and brushed by a brush made of nylon or mohair. As a result, particle contaminant on the wafer surface is brushed off and removed.
When the main surface of a wafer for forming semiconductor devices is treated, since the rear surface of the wafer is attached to a chuck, the chuck uses a vacuum suction pad. On the other hand, when the rear surface of the wafer is treated, since semiconductor devices formed on the main surface of the wafer must be prevented from being damaged, a grip chuck having three or more clamps for abutting the edge of the wafer is used. An example of the grip chucks is disclosed in Jpn. Pat. Appln. KOKOKU Publication No. 3-9607.
In the grip chucks, where the main surface of a wafer is directed downward, it is necessary to protect the main surface from a treatment liquid supplied to the rear surface (the upper surface). Similarly, when both surfaces of a wafer need to be cleaned, if the surfaces are consecutively cleaned, it is necessary to protect a first surface, which has been cleaned first, from the cleaning liquid for cleaning a second surface. For this purpose, in a conventional cleaning apparatus, a protecting gas (e.g., N.sub.2 gas) is supplied to the lower surface of the wafer to prevent a cleaning liquid from flowing to the lower surface.
However, in the spin chucks, a driving mechanism for rotating a wafer, a clamp driving mechanism and a supplying mechanism for supplying a protecting gas must be arranged coaxial. Therefore, the structure is rendered complicated. In addition, since two driving sources are required, the apparatus is inevitably large in size.